Many applications such as filters, catalyst carriers or tissue scaffolds require highly porous, yet mechanically strong scaffolds whose micro- and nanoarchitectures can be carefully tailored. Because the introduction of porosity significantly lowers the mechanical properties of a material, it is difficult to achieve a successful compromise between porosity and mechanical performance. Furthermore, it is a great challenge to modify structure and mechanical performance independently.
Certain particles generated by some nuclear reactions in breeder and burner reactors, including alpha particles, have short range with desired energy in nuclear fuels. When these particles are desirable as reactants in additional reactions, is desirable to position nuclei that generate the particles at predetermined distances from the nuclei that are reactants in the additional reactions. It is therefore desirable to position particular isotopes in nuclear fuels with precision within particular portions of individual fuel rods, or pins, in order to promote desired nuclear reactions over less desirable reactions. Further, many nuclear reactions may generate gasses that can cause swelling of a rod or pin. It can therefore be desirable to have a porous central portion within a nuclear fuel rod or pin in order to vent these gasses.
In a typical fast reactor, pressurized water reactor (PWR) or boiling water reactor (BWR) fuel design, a 6-10 mm diameter fuel rod or pin has fuel pellets of 92-95% theoretical density surrounded by a 0.1 mm helium or sodium-filled gap and housed in a cladding tube of about 0.4 mm in thickness. Fuel rods or pins of similar dimensions used in other types of light-water reactors often have similar requirements and dimensions.